In the case where H-shaped steel is produced, a material, such as a slab or a bloom, extracted from a heating furnace is shaped into a raw blank (a material to be rolled with a so-called dog-bone shape) by a rough rolling mill (BD). Thicknesses of a web and flanges of the raw blank are subjected to reduction by an intermediate universal rolling mill, and moreover, flanges of a material to be rolled are subjected to width reduction and forging and shaping of end surfaces by an edger rolling mill close to the intermediate universal rolling mill. Then, an H-shaped steel product is shaped by a finishing universal rolling mill.
In such a method for producing H-shaped steel, a technology is known (e.g., see Patent Literature 1) in which, in shaping a raw blank with a so-called dog-bone shape from a slab material having a rectangular cross-section, splits are created on slab end surfaces in a first caliber of a rough rolling step, the splits are then widened or made deeper and edging rolling is performed in a second caliber and subsequent calibers, and the splits on the slab end surfaces are erased in subsequent calibers.
In addition, for example, Patent Literature 2 discloses a technology of forming flange-corresponding portions of H-shaped steel by creating splits on slab end surfaces, sequentially making the splits deeper, and then expanding the splits in a box caliber.